A drop of old tuberculin, which is an extract of tubercle bacilli, is put on the skin and then a small superficial scarification is made by turning, with some pressure, a vaccination lancet on the surface of the skin. The next day only those individuals show an inflammatory reaction at the point of vaccination who have already been infected with tuberculosis, whereas the healthy individuals show no reaction at all. Every time we find a positive reaction, we can say with certainty that the child is tuberculous.

'The Relation of Tuberculosis to Infant Mortality', read at the third mid-year meeting of the American Academy of Medicine, New Haven, Conn, (4 Nov 1909). In Bulletin of the American Academy of Medicine (1910), 11, 75.

In the first papers concerning the aetiology of tuberculosis I have already indicated the dangers arising from the spread of the bacilli-containing excretions of consumptives, and have urged moreover that prophylactic measures should be taken against the contagious disease. But my words have been unheeded. It was still too early, and because of this they still could not meet with full understanding. It shared the fate of so many similar cases in medicine, where a long time has also been necessary before old prejudices were overcome and the new facts were acknowledged to be correct by the physicians.

In the Mortality Bills, pneumonia is an easy second, to tuberculosis; indeed in many cities the death-rate is now higher and it has become, to use the phrase of Bunyan 'the captain of the men of death.'

Professor von Pirquet has come to this country exactly at the right time to aid us. He has shown us how to detect tuberculosis before it has become so developed as to be contagious and has so taken hold of the individual as to be recognized by any other means. In thousands of cases I for my part am unable to detect tuberculosis in infancy or early childhood without the aid of the tuberculin test which Prof. von Pirquet has shown to be the best. He has taught us how by tubercular skin tests, to detect it. ... What Dr. von Pirquet has done already will make his name go down to posterity as one of the great reformers in tuberculin tests and as one who has done an immense amount of good to humanity. The skin test in twenty-four hours will show you whether the case is tubercular.

Discussion on 'The Relation of Tuberculosis to Infant Mortality', read at the third mid-year meeting of the American Academy of Medicine, New Haven, Conn, (4 Nov 1909). In Bulletin of the American Academy of Medicine (1910), 11, 78.

Srinivasa Ramanujan was the strangest man in all of mathematics, probably in the entire history of science. He has been compared to a bursting supernova, illuminating the darkest, most profound corners of mathematics, before being tragically struck down by tuberculosis at the age of
33... Working in total isolation from the main currents of his field, he was able to rederive 100 years worth of Western mathematics on his own. The tragedy of his life is that much of his work was wasted rediscovering known mathematics.

To prove that tuberculosis is caused by the invasion of bacilli, and that it is a parasitic disease primarily caused by the growth and multiplication of bacilli, it is necessary to isolate the bacilli from the body, to grow them in pure culture until they are freed from every disease product of the animal organism, and, by introducing isolated bacilli into animals, to reproduce the same morbid condition that is known to follow from inoculation with spontaneously developed tuberculous material.

In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion.
(1987) -- Carl Sagan